The neural control of cyclic processes, such as locomotion, consists of a dynamic interaction among spinal pattern-generator circuits, supraspinal centers, and afferent signals. The present understanding of neural control systems, which is limited, has been based primarily upon results of experimental studies that have sometimes been complemented by modeling studies. Experimental investigations of the neural mechanisms that generate locomotor behavior might benefit greatly from a device that could provide real-time interaction between complex realistic models and actual biological systems. In a setup such as this, where the model parameters are well-characterized and can be accurately manipulated, the influence of specific mechanisms in shaping the output of the biological system can be investigated. To be used in this manner, the device must be able to simulate the behavior of complex neural circuits in real-time, the behavior of the device must be well-characterized, and the device must be interfaced with an actual neural system. Research is proposed to develop a neuromorphic analog very large scale integrated (VLSI) circuit that is based on a mathematical model of the lamprey central pattern generator that can be interfaced, in real-time, with the in-vitro lamprey spinal cord preparation. The proposed project will include: 1) the design, development and analysis of an analog VLSI circuit implementation of a single segment of the lamprey spinal pattern generator; 2) experimental studies on the isolated lamprey spinal cord to characterize its response to periodic perturbation; 3) implementation and analysis of a mathematical model of the lamprey spinal cord to guide the analog VLSI circuit design and to assist in the interpretation of experimental results; and 4) experimental studies in which the analog VLSI circuit will be interfaced directly with the isolated lamprey spinal cord. Successful completion of this project is intended to result in the production of a device that would provide a unique opportunity for experimental neurophysiologists to effectively utilize real-time implementations of neural models. Future work will be directed at enhancing the neurobiological fidelity of this analog VLSI circuit and at improving its interface with the biological system.